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प्रश्न
For the G.P. `1/27, 1/9, 1/3, ........., 81`; find the product of fourth term from the beginning and the fourth term from the end.
उत्तर
Given G.P. : `1/27, 1/9, 1/3, ........., 81`
Here,
Common ratio, r = `(1/9)/(1/27)` = 3
First term, a = `1/27` and last term, l = 81
∴ 4th term from the beginning = ar3
= `1/27 xx (3)^3`
= `1/27 xx 27`
= 1
And 4th term from an end = `1/r^3`
= `81/(3)^3`
= `81/27`
= 3
Thus, required product = 1 × 3 = 3
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